The present invention relates to fiber optic coupled pressure transducers and to methods of fabrication thereof. More specifically, the invention relates to miniaturized pressure measurement apparatus, such as intravascular catheter tip fiber optic pressure sensors, and to mass production techniques permitting low unit cost production of such apparatus.
Measurement of intravascular blood pressure by means of a hollow catheter tube filled with saline solution and attached to an external transducer has been largely supplanted by fiber optic coupled catheter tips incorporating a pressure transducer. The prior art encompassing the latter includes fiber optic pressure sensors in which a reflecting, pressure deformable diaphragm at the end of a catheter tip is spaced a small distance from the end of a fiber bundle and modulates the light reflected back through the fibers in accordance with the pressure responsive position of the diaphragm.
An example of such a catheter tip pressure sensor is shown in U.S. Pat. No. 4,487,206 wherein three optic fibers extend through a hollow catheter tube to a lens element at the terminal ends of the fibers within a sensor tip. Light transmitted from a source outside the tube through one fiber is directed to a pressure responsive, reflecting surface which modulates the focal length of the lens-mirror-diaphragm combination. Light returning through the other two fibers is sensed by reference and signal sensor detectors, respectively, permitting the development of a pressure-indicative signal. It is desirable, of course, to make the catheter tubes and tips as small as possible in such applications, provided the required level of accuracy and reliability of operation are maintained. Also within the necessary limits of accuracy and reliability, the apparatus should be as simple and economical as possible to fabricate, operate and service.
It is a principal object of the present invention to provide a fiber optic coupled pressure transducer of extremely small diameter which is easy and relatively cheap to manufacture and, at the same time, highly accurate and reliable.
It is a further object to provide a miniaturized, intravascular, fiber optic pressure sensor which may be fabricated at a cost which permits disposal of portions of the sensor after each use.
A more specific object is to provide a fiber optic coupled pressure measurement system requiring only a single optic fiber for carrying light both transmitted to and reflected from a pressure responsive diaphragm.
Still another object is to provide a disposable (single use) intravascular catheter tip of compact design which is defibrillator proof, with low artifact generation and relatively broad manufacturing tolerances.
A still further object is to provide a novel method of manufacturing fiber optic catheter tips for use in intravascular blood pressure monitoring.
Another object is to provide a fiber optic, intravascular, blood pressure measuring unit which is compatible with all currently available monitors, irrespective of the type of excitation voltage supplied.
Other objects will in part be obvious and will in part appear hereinafter.